This invention relates to a positive-type photosensitive resin composition having strong UV light absorption and a process for forming a pattern using the same.
As fine processing technique for semiconductor elements, there is widely employed pattern formation using a positive-type photosensitive resin composition and a g-line (light of 436 nm) projection aligner. In order to improve the resolving power of a photosensitive resin, there are employed an improvement of the photosensitive resin and an improvement of a light exposing device. The light exposing device can be improved by increasing the numerical aperture of lens or making the exposing wavelength shorter. The resolving power is proportional to the exposing wavelength and can be improved by about 16% by changing the g-line to i-line (light of 365 nm). A light exposing device using a shorter wavelength of near 250 nm is now under development, but it requires a much more time to accomplish such a device.
Thus, a light exposing device using i-line is noticed. As a photosensitive resin used in such a device, there is used a composition comprising a novolak resin and 1,2-naphthoquinone-(2)-diazido-sulfonic acid ester as a photosensitizer (e.g. Japanese Patent Examined Publication Nos. 37-18015 and 54-20330, and Japanese Patent Unexamined Publication Nos. 62-28457 and 62-89040). Such a photosensitive resin composition can be used on a silicon oxide film and silicon nitride film, but it causes a problem of narrowing of patterns due to reflected light when used on a substrate having a high light reflectance such as an aluminum film.